This invention relates to the production of pre-cooked, shelf-stable, filled pasta products such as ravioli, lasagna, manicotti and the like. More particularly this invention relates to the production of novel, filled, hydrated pasta products which can be thermally processed to render the products commercially-sterile without adversely affecting the color, texture or appearance of the filling.
As used herein, the term "commerciallv-sterile" means (a) the absence of microorganisms capable of growing in and spoiling the food under normal non-refrigerated storage conditions, and (b) the absence of pathogenic microorganisms capable of proliferating in the food.
In order to facilitate the use of cheese-filled pasta products in the home, pasta product such as lasagna and ravioli have been offered in pre-cooked, shelf-stable or pre-cooked, frozen form, typically packaged with a tomato sauce. The frozen forms of these products have generally been regarded as preferred from a quality perspective since frozen products do not undergo severe heat treatment; however, frozen products are more costly to distribute and store and require relatively long heating times prior to serving. Pre-cooked, shelf-stable products must be retorted in sealed containers under time temperature conditions sufficient to provide a commercially-sterile product. The sealed containers have historically been of the metal can type. More recently there have appeared plastic bowls and trays which are sealed with flexible sheet material. The present invention is applicable to both types of containers.
In the case of cheese lasagna, cheese manicotti and cheese ravioli it has been found that when conventional, ricotta and/or mozzarella cheese fillings are subjected to a retort step (e.g., 240.degree. F. or higher for times of about one hour), the color of the filling changes from white to tan or brown. This darkened color, which seems to result from carmelization of lactose and which may be accompanied by an adverse flavor effect, is a significant negative in the eyes of consumers. It is known that, if food products are formulated to a high-acid pH of below about 4.6, it is possible to achieve commercial sterility in a retort at temperatures of about 185.degree.-200.degree. F.; however, even at these less severe conditions, conventional, ricotta and/or mozzarella cheese fillings still undergo undesirable color darkening.
As discussed in U.S. Pat. No. 3,628,969 to Vilian, various attempts have been made to improve the retort-stability of starch and milk containing food products. Heretofore, however, it has not been possible to stabilize conventional cheese fillings nor have retort-stable substitutes for these fillings been identified.